Before the evolution of wolf into dog, it is posited that man and wolf worked together hunting game. Wolves were the superior tracker but man was the superior killer, thus wolves would lead man to the prey and man would leave some of the meat to the wolves. This working relationship eventually led to the evolution of dogs, although there is controversy as to the exact nature of that transition. Some say wolves evolved naturally into dogs, wherein the wolves that worked best with humans slowly began to assimilate and pass their domesticated genes down. Others say that humans took wolf pups and raised them to be domesticated. Either way, humans and dogs formed a working relationship.[1]

In Homer's Odyssey (c. 8th century BC), upon Odysseus' return, his beloved dog Argos is the only individual to recognize him. Odysseus anonymously asks his old friend, "Eumaeus, what a noble hound that is over yonder on the manure heap: his build is splendid; is he as fine a fellow as he looks, or is he only one of those dogs that come begging about a table, and are kept merely for show?" "This dog," answered Eumaeus, "belonged to him who has died in a far country. If he were what he was when Odysseus left for Troy, he would soon show you what he could do. There was not a wild beast in the forest that could get away from him when he was once on its tracks. But now he has fallen on evil times, for his master is dead and gone, and the women take no care of him." Unable to greet his beloved dog, as this would betray who he really was, Odysseus passes by (but not without shedding a tear) and entered the well-built mansion, and made straight for the riotous pretenders in the hall. But Argos passed into the darkness of death, now that he had fulfilled his destiny of faith and seen his master once more after twenty years. This story shows both companionship and neglect towards dogs amongst humans.

Giving up all their belongings and ties, the Pandavas, accompanied by a dog, made their final journey of pilgrimage to the Himalayas. Yudhisthira was the only one to reach the mountain peak in his mortal body, because he was unblemished by sin or untruth. On reaching the top, Indra asked him to abandon the dog before entering the Heaven. But Yudhisthira refused to do so, citing the dog's unflinching loyalty as a reason. It turned out that the dog was his god-father, Dharma. The incident symbolized that dharma follows you till the end.

Previous to the 19th century, dogs, other than lap dogs, were largely functional. Used for activities such as hunting, watching and guarding, language describing the dog often reflected these positions within society. According to the Oxford English Dictionary, “In the oldest proverbs and phrases dogs are rarely depicted as faithful or as man’s best friend, but as vicious, ravening, or watchful.” Beginning in the 18th century, multiplying in the 19th and flourishing in the 20th century, language and attitudes towards dogs began to shift. Possibly, this societal shift can be attributed to discovery of the rabies vaccine in 1869.[2]

The earliest citation of the actual word choice - in English - is traced to a poem printed in the The New-York Literary Journal, Volume 4, 1821:[3]

In 1870 Warrensburg, Missouri, George Graham Vest represented a farmer suing for damages after his dog, Old Drum, had been shot and killed. Vest’s closing speech included this quote, “The one absolutely unselfish friend that a man can have in this selfish world, the one that never deserts him and the one that never proves ungrateful or treacherous is his dog.” In 1958, a statue of Old Drum was erected on the Johnson County Courthouse lawn containing a summation of Vest’s closing speech, “A man’s best friend is his dog.”[5][6]